Detailed studies of protein synthesis during oogenesis, preimplantation development, and early postimplantation development will be undertaken using one and two-dimensional polyacrylamide gel electrophoretic systems. Comparisons will be carried out between protein synthesis in early embryos and in cultured teratocarcinoma cells. X-chromosome expression will be analyzed in preimplantation embryos and in cultured teratocarcinoma cells, and specific mutations affecting preimplantation embryonic development will be analyzed.